Suspicious PowerShell Engine ImageLoad

  1[metadata]
  2creation_date = "2020/11/17"
  3integration = ["endpoint"]
  4maturity = "production"
  5updated_date = "2026/05/04"
  6
  7[rule]
  8author = ["Elastic"]
  9description = """
 10Identifies the PowerShell engine being invoked by unexpected processes. Rather than executing PowerShell functionality
 11with powershell.exe, some attackers do this to operate more stealthily.
 12"""
 13from = "now-9m"
 14index = ["logs-endpoint.events.library-*"]
 15language = "kuery"
 16license = "Elastic License v2"
 17name = "Suspicious PowerShell Engine ImageLoad"
 18note = """## Triage and analysis
 19
 20### Investigating Suspicious PowerShell Engine ImageLoad
 21
 22PowerShell is one of the main tools system administrators use for automation, report routines, and other tasks. This makes it available for use in various environments, and creates an attractive way for attackers to execute code.
 23
 24Attackers can use PowerShell without having to execute `PowerShell.exe` directly. This technique, often called "PowerShell without PowerShell," works by using the underlying System.Management.Automation namespace and can bypass application allowlisting and PowerShell security features.
 25
 26#### Possible investigation steps
 27
 28- Investigate the process execution chain (parent process tree) for unknown processes. Examine their executable files for prevalence, whether they are located in expected locations, and if they are signed with valid digital signatures.
 29- Investigate abnormal behaviors observed by the subject process, such as network connections, registry or file modifications, and any spawned child processes.
 30- Investigate other alerts associated with the user/host during the past 48 hours.
 31- Inspect the host for suspicious or abnormal behavior in the alert timeframe.
 32- Retrieve the implementation (DLL, executable, etc.) and determine if it is malicious:
 33  - Use a private sandboxed malware analysis system to perform analysis.
 34    - Observe and collect information about the following activities:
 35      - Attempts to contact external domains and addresses.
 36      - File and registry access, modification, and creation activities.
 37      - Service creation and launch activities.
 38      - Scheduled task creation.
 39  - Use the PowerShell `Get-FileHash` cmdlet to get the files' SHA-256 hash values.
 40    - Search for the existence and reputation of the hashes in resources like VirusTotal, Hybrid-Analysis, CISCO Talos, Any.run, etc.
 41
 42### False positive analysis
 43
 44- This activity can happen legitimately. Some vendors have their own PowerShell implementations that are shipped with some products. These benign true positives (B-TPs) can be added as exceptions if necessary after analysis.
 45
 46### Response and remediation
 47
 48- Initiate the incident response process based on the outcome of the triage.
 49- Isolate the involved hosts to prevent further post-compromise behavior.
 50- If the triage identified malware, search the environment for additional compromised hosts.
 51  - Implement temporary network rules, procedures, and segmentation to contain the malware.
 52  - Stop suspicious processes.
 53  - Immediately block the identified indicators of compromise (IoCs).
 54  - Inspect the affected systems for additional malware backdoors like reverse shells, reverse proxies, or droppers that attackers could use to reinfect the system.
 55- Remove and block malicious artifacts identified during triage.
 56- Investigate credential exposure on systems compromised or used by the attacker to ensure all compromised accounts are identified. Reset passwords for these accounts and other potentially compromised credentials, such as email, business systems, and web services.
 57- Run a full antimalware scan. This may reveal additional artifacts left in the system, persistence mechanisms, and malware components.
 58- Determine the initial vector abused by the attacker and take action to prevent reinfection through the same vector.
 59- Using the incident response data, update logging and audit policies to improve the mean time to detect (MTTD) and the mean time to respond (MTTR).
 60"""
 61
 62setup = """## Setup
 63
 64This rule is designed for data generated by [Elastic Defend](https://www.elastic.co/security/endpoint-security), which provides native endpoint detection and response, along with event enrichments designed to work with our detection rules.
 65
 66Setup instructions: https://ela.st/install-elastic-defend
 67"""
 68
 69references = ["https://www.elastic.co/security-labs/elastic-security-labs-steps-through-the-r77-rootkit"]
 70risk_score = 47
 71rule_id = "852c1f19-68e8-43a6-9dce-340771fe1be3"
 72severity = "medium"
 73tags = [
 74    "Domain: Endpoint",
 75    "OS: Windows",
 76    "Use Case: Threat Detection",
 77    "Tactic: Execution",
 78    "Resources: Investigation Guide",
 79    "Data Source: Elastic Defend",
 80]
 81timestamp_override = "event.ingested"
 82type = "new_terms"
 83
 84query = '''
 85host.os.type:windows and event.category:library and
 86  dll.name:("System.Management.Automation.dll" or "System.Management.Automation.ni.dll") and
 87  not (
 88    process.code_signature.subject_name:(
 89      "Microsoft Corporation" or
 90      "Microsoft Dynamic Code Publisher" or
 91      "Microsoft Windows"
 92    ) and process.code_signature.trusted:true and not process.name.caseless:"regsvr32.exe"
 93  ) and
 94  not (
 95    process.executable:(C\:\\Program*Files*\(x86\)\\*.exe or C\:\\Program*Files\\*.exe) and
 96    process.code_signature.trusted:true
 97  ) and
 98  not (
 99    process.executable: C\:\\Windows\\Lenovo\\*.exe and process.code_signature.subject_name:"Lenovo" and
100    process.code_signature.trusted:true
101  ) and
102  not (
103    process.executable: C\:\\Windows\\AdminArsenal\\PDQInventory-Scanner\\service-*\\exec\\PDQInventoryScanner.exe and
104    process.code_signature.subject_name:"PDQ.com Corporation" and
105    process.code_signature.trusted:true
106  ) and
107  not (
108    process.name: (_is*.exe or "DellInstaller_x64.exe") and
109    process.code_signature.subject_name:("Dell Technologies Inc." or "Dell Inc" or "Dell Inc.") and
110    process.code_signature.trusted:true
111  ) and
112  not (
113    process.executable: C\:\\ProgramData\\chocolatey\\* and
114    process.code_signature.subject_name:("Chocolatey Software, Inc." or "Chocolatey Software, Inc") and
115    process.code_signature.trusted:true
116  ) and
117  not (
118    process.name: "Docker Desktop Installer.exe" and
119    process.code_signature.subject_name:"Docker Inc" and
120    process.code_signature.trusted:true
121  ) and
122  not process.executable : (
123    "C:\\Windows\\System32\\WindowsPowerShell\\v1.0\\powershell.exe" or
124    "C:\\Windows\\SysWOW64\\WindowsPowerShell\\v1.0\\powershell.exe"
125  )
126'''
127
128
129[[rule.threat]]
130framework = "MITRE ATT&CK"
131[[rule.threat.technique]]
132id = "T1059"
133name = "Command and Scripting Interpreter"
134reference = "https://attack.mitre.org/techniques/T1059/"
135[[rule.threat.technique.subtechnique]]
136id = "T1059.001"
137name = "PowerShell"
138reference = "https://attack.mitre.org/techniques/T1059/001/"
139
140
141
142[rule.threat.tactic]
143id = "TA0002"
144name = "Execution"
145reference = "https://attack.mitre.org/tactics/TA0002/"
146
147[rule.new_terms]
148field = "new_terms_fields"
149value = ["process.executable"]
150[[rule.new_terms.history_window_start]]
151field = "history_window_start"
152value = "now-5d"